How long can a bottle of wine last if it is removed from "cellar conditions" but not opened? Where I live the temperature is usually in the 70's. I guess this applies to wine in stores as well as at home...

That's difficult to answer. Prolonged temperatures above 72 degrees can damage a wine or at least age it quicker than you may wish. A few weeks or even months at 70-75 may have no effect but one afternoon in a car trunk where temperature is in the 80's or 90's may "cook" the wine. Some wines seem to be more resistant to heat damage than others. Burgundies/Pinot Noirs (cool climate wines) may suffer more readily than Spanish reds or Southern France wines which come from a warmer climate. Some of my wines are kept in a 55-degree wine storage unit but others are lying flat in boxes at room temperature of 68-74 degrees. I accept that they may age more readily but since I don't have wines going back to the 1970's or 1980's, I can anticipate drinking them in the next few years--not holding them for 20 years.